Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

296 •DOG OWNER’S HOME VETERINARY HANDBOOK
Some plants and herbs can also cause liver failure; these include ragwort,
certain mushrooms, and blue-green algae. Molds such as aflatoxin, which
grows on corn and may contaminate foods, can cause severe liver damage.
A blockage of the bile duct by gallstones, liver flukes, tumors, or pancreatitis
is uncommon, but becomes a consideration when a dog has unexplained
jaundice.
Treatment: Blood tests, including bile acid assay, ultrasound, and CT scan,
provide useful information, but the only definitive test is biopsy of the liver.
The prognosis for recovery depends on how long the dog has been ill, the
extent of liver damage, and whether the disease can be surgically cured or
controlled with medications.
Infectious diseases respond to treatment of the underlying condition. Drugs
and poisons frequently exert temporary effects that are reversed when the
exposure is stopped. Bile duct obstructions and some primary tumors of the
liver can be corrected by surgery.
In addition to treating the liver disease, it is important to control and prevent
complications, particularly hepatic encephalopathy and bleeding. This
may involve feeding a special diet that is low in protein, lowering blood
ammonia levels, maintaining blood-clotting factors, preventing seizures, correcting
electrolyte abnormalities, and administering antacids to prevent
stomach and duodenal ulcers. Supplements such as SAM-e and milk thistle
are useful in both restoring and maintaining normal liver function.
Liver Shunt
Liver shunts, also called portosystemic shunts, are abnormal veins that enable
blood from the intestines to bypass the liver. Ammonia and other toxins are
not metabolized or removed from the circulation, resulting in signs of hepatic
encephalopathy.
The majority of portosystemic shunts are congenital. Multiple shunts outside
the liver may be congenital but are more often caused by cirrhosis. Dogs
of a variety of breeds have been identified with liver shunts, but Miniature
Schnauzers, Maltese, and Yorkshire Terriers appear to be at increased risk for
congenital shunts that develop outside the liver. Large-breed dogs, such as
Irish Wolfhounds, are at increased risk for shunts inside the liver that occur
because a fetal vein that normally closes at birth fails to do so. Most dogs with
congenital liver shunts develop symptoms of hepatic encephalopathy by 6
months of age, although some dogs may not develop symptoms until middle
age or older. The diagnosis is confirmed by X-ray studies where contrast dyes
are injected into the liver circulation, and by bile acid assays. Ultrasound may
also be useful. These studies are available at referral centers.
Treatment: The treatment of choice for liver shunts is partial or complete
surgical ligation of the shunt. This is not always possible. Medical management